It is now common practice to explore the oceans of the earth for deposits of oil, gas and other valuable minerals by seismic techniques in which an exploration vessel imparts an acoustic wave into the water, typically by use of a compressed air "gun." The acoustic wave travels downwardly into the sea bed and is reflected at the interfaces between layers of materials having varying acoustic impedances. The wave travels back upwardly where it is detected by microphone or "hydrophone" elements in a streamer towed by the vessel to yield information regarding characteristics of the underwater material and structures.
A towed streamer comprises a plurality of pressure-sensitive hydrophone elements enclosed within a waterproof jacket and electrically coupled to recording equipment onboard the vessel. Each hydrophone element within the streamer is designed to convert the mechanical energy present in pressure variations surrounding the hydrophone element into electrical signals. Due to its often extreme length (on the order of kilometers), the streamer is divided into a number of separate sections or "modules" that can be decoupled from one another and that are individually waterproof. Individual streamers can be towed in parallel through the use of paravanes to create a two dimensional array of hydrophone elements. Data buses running through each of the modules in the streamer carry the signals from the hydrophone elements to the recording equipment (so-called "acoustic data").
In addition to acoustic data, it is also important to collect and transmit data concerning operational status of the array to the vessel (so-called "nonacoustic data"). Nonacoustic data comprises physical characteristics of interest regarding the operation of each module, including whether water has invaded a module in the streamer, module temperature, module depth and power supply voltage.
Today, many towed arrays have digital data channels. The primary advantage of digital data transmission is its ability to handle a significantly greater number of sensors for a given streamer size. For example, streamers with a thousand or more sensors would be of an impractical large diameter to simply contain the analog bus conductors therein. Also, with digital data transmission, data transmission rates are higher and, with proper attention to shielding of electromagnetic interference, data fidelity is maintained from the hydrophone to the recording equipment.
While under tow, towed arrays undergo stretching forces on the order of several thousand pounds. These forces must be transmitted through and between each module.
Accordingly, what is needed in the art is an improved coupler for joining two modules of a towed array together. The coupler must not only provide for mechanical transmission of significant towing forces but must also provide low noise electrical coupling between the modules so sensitive digital data may be transferred therebetween.